Icefin is a custom designed remotely or autonomously operated vehicle (ROV/AUV) for sub-ice deployments in polar environments with a primary focus on modularity for deploying multiple payloads throughout a season to characterize the under-ice environment. Over the past six years the vehicle has undergone numerous design improvements to become a stable and robust platform. The current primary vehicle design was proven during the 2018 field campaign. With the success of that season, a second vehicle was built to accommodate two field campaigns in austral summer 2019–2020, wherein the vehicle dual Icefin vehicles were deployed through ~600m hot water drilled boreholes to investigate the grounding zones of Thwaites Glacier and the Ross Ice Shelf. Presented here is an overview of the engineering design updates that were incorporated from the 2017 season. Also presented are results and lessons learned from the 2019 deployments.